Probing Compressed Top Squarks at the LHC at 14 TeV

A feasibility study is presented for the search of the lightest top squark ($t$) in a compressed scenario, where its mass is approximately equal to the sum of the masses of the top quark and the lightest neutralino $\tilde\chi^0_1$ and there exists no limit from the current 8-TeV data or from the 14-TeV projections. The study is performed in the final state of two $b$-jets, one lepton, large missing transverse energy, and two energetic jets with a large separation in pseudo-rapidity, in opposite hemispheres, and with large dijet mass. The analysis shows that the LHC could probe compressed top squarks mass $\sim 300$ GeV with an integrated luminosity of $300$ fb$^{-1}$ for two ($t$+$\tilde\chi^0_1$) and three body ($b$+$W$+$\tilde\chi^0_1$) final states arising from the stop decay at $5\sigma$ significance with no systematic uncertainty. After including the systematics, the significance for $m_{st}$ = 200 GeV and $\Delta M=7$ GeV is expected to be 6(3)$\sigma $ for 300 fb$^{-1}$ luminosity with 3(5)\% systematic uncertainty, while the significance becomes 4(2)$\sigma$ for the same top squark mass with $\Delta M = -7$ GeV.